Question 🙋: best public transport app for Australia or Melbourne?

Good day! I'll be flying to Australia soon, and I'm interested in trying public transport (even if it's good or not always good, I want to see what's there). Which apps would you recommend?

// I've tried googling the question, but somehow get 20-minute videos with animated characters and nonsense like that. I think I'll trust recommendations from this community by a lot more 💚.

I'll be in Melbourne, Adelaide and Sydney.